#include <iostream>
using namespace std;

const double PI = 3.14;
void getArea(double raidus, double& result)
{
    result = raidus * PI * raidus;
}

int main(int argc, char const *argv[])
{
    /* code */
    double radius, result = 0;
    cout << "Please input a number" << endl;
    cin >> radius;
    getArea(radius, result);
    cout << "Area is " << result << endl;
    return 0;
}
